Airplane traffic controlling system



July 5, 1949. S. P. SAINT 2,475,256

AIRPLANE TRAFFIC CONTROLLING SYSTEM Filed May 15, 1942 3 Sheets-Sheet lQ m. u. m g m x3 T ,JKEM 1 July 5, 1949. s. P. SAINT 2,475,256

AIRPLANE TRAFFIC CONTROLLING SYSTEM Filed May 15, 1942 s Sheds-Sheet 2FBG.3. FIG. 4.

ATTORNEY Jun) 5, 1949. s, sA|NT 2,475,256

AIRPLANE TRAFFIC CONTROLLING SYSTEM Filed May 15, 1942 3 Sheets-Sheet 3n: new 010 F 1&5.

'INVENTOR ATTORNEY Patented July 5, 1949 AIRPLANE TRAFFIC CONTROLLINGSYSTEM Samuel P. Saint, Port Washington, N. Y., assignor to GeneralRailway Signal Company, Rochester,

Application May 15, 1942, Serial No. 443,116

6 Claims. 1

This invention relates in general to airplane traflic controllingsystems, and has more particular reference to a system for controllingthe flight of planes between, and the approach of planes to, airports,and the safe landing of planes at airports.

Airports may be located in such country that approaching planesencounter various hazards before reaching them. The hazards may be tallbuildings, towers, hills or the like, and unless some safe signallingsystem be employed for guiding the planes, they must fly, in theinterest of safety, more than sufficiently high to clear theobstructions. In many cases, particularly under conditions of poorvisibility, the planes must approach at such high levels that landing isdifficult and may require several attempts before being effected.

Furthermore, after a plane has reached an airport, there is possibilityof confustion in identifying the runway to be employed, which runwaysare generally outlined by marking lights.

It is proposed, in accordance with this invention, to employ a rotatinglight signal displaying a pluralit of colored light beams, so as tofurnish a guide for any plane approaching the airport or other location.The rotating light is also to be raised and lowered, in accordance withthe hazards surrounding approach to the airport, or other location, soas to properly define a path clearing such hazards.

It is also proposed, in accordance with this invention, to designate therunways or air routes by a plurality of light signals, each of whichdisplays a beam having a plurality of colored portions so as todistinctively designate the runway, and, furthermore, to form an easilyidentified glide path for guiding a descending plane to safely land atthe proper point on the runway.

Further objects, purposes, and characteristic features of this inventionwill appear as the description progresses, reference being made to theaccompanying drawings, showing, solely by way of example, and in nomanner whatsoever in a limiting sense, a plurality of forms which theinvention can assume. In the drawings:

Fig. 1 is a diagrammatic, plan view of an airport and its surroundings.

Fig. 2 is a diagrammatic, elevational view of the airport of Fig. 1.

Fig. 3 is a fragmentary, diagrammatic, sectional view, with parts shownin elevation, of a rotating signal such as employed in this invention.

Fig. 4 is a sectional view, on an enlarged scale, of the rotating signalof Fig. 3.

Fig. 5 is a diagrammatic, elevational view of runway signal means, to anenlarged scale, in accordance with this invention.

Fig. 6 is a diagrammatic fragmentary sectional view of a runway signaland associated runway.

Fig. 7 is a circuit diagram in accordance with this invention.

Fig. 8 is a diagrammatic plan view of a modified form of runway signaland the associated runway.

Fig. 9 is a sectional elevation with parts in elevation, on line 9-9 ofFig. 8, viewed in the direction of the arrows.

Referring now to the drawings, and first to Fig. 1, there is here shown,in a wholly diagrammatic fashion, an airport I, having a plurality ofdifferently directed landing runways 2, 3, 4, 5, 6, l, 8 and 9. Suitablylocated on the landing field, and preferably more or less centrally, isa light signal S, mounted on a mast ii, if desired.

The runways 2, 3, etc. will be employed in the usual way for planes toland when traveling into the wind, and, thus, one or another of themwill be used at any particular time, in accordance with weatherconditions. Each runway has embedded in it, and preferablylongitudinally centrally thereof, two signal lamps, such as lamps l2 and13 for runway 5, and constructed and directed as described below. Merelby way of example, there has been shown at the left of the landing fieldan obstruction in the form of a tree l4, while at the right is arelatively distant obstruction in the form of rising ground forming ahill 15, and a nearer obstruction in the form of tree I5 A port buildingI0 is also located to the left of the landing field.

It is clear that if no signalling system be employed, an approachingplane, under conditions of low visibility, in the interest of safetywill generally approach the field from an elevation higher than isreally necessary, and, hence, to land, it may be necessary to makeseveral attempts, whereas with a proper signalling system, the hazardcan be safely avoided, by just a safe margin, and landing can be verygreatly facilitated.

The rotating signal S is shown in greater detail in Figs. 3 and 4. Thissignal is constituted by a base B, which, through legs 18, supports amotor M, of any desired constant speed type, such as a synchronousmotor. This motor, through gears 96 and I6, drives a verticallypositioned shaft ll, passing loosely through a cam C, which is supportedon, and fixed to a housing I8 carried on legs I 8. The shaft I! haspivoted to it as at I8 an offset arm 19, which carries the signal S.

Lead-in wires 20 are connected, as shown, to supply the motor and thesignal with energy, which can be either alternating or direct, depend--ing upon the type of motor, and signal employed. Signal S is supportedby an arm 2!, carrying a roller 22, which rolls on the cam surface 23,of cam C, as the signal is rotated by the motor.

Cam C is formed, as shown, to conform with the topography ofthe countryimmediately surrounding the airport. For example, the cam has arelatively high portion 24, positioned to tilt the signal S more steeplyupwardly, when in its rotation it is directed toward hill [5, andanother relatively high portion 25, positioned to tilt the signal moresteeply upwardly, when it is directed toward tree M. In this manner, thevarious hazards surrounding the airport, and constituting danger pointsfor an approaching plane, can be translated into hills and valleys oncam C, so that signal S, in its rotation, will rise and fall andmaintain a predetermined elevation above the various approach obstacles.

As shown in Fig. 4, the signal is constituted by a casing 26, and alight source 21, positioned at the focus of a parabolic reflector 28whereby light rays are directed forwardly out of the signal in aparallel beam by the reflector. Closing the front end of casing 26, is alens L, formed with a smooth convex outer surface 29, and a horizontallypositioned fluted prismatic surfaced inner face. These curved prismaticfaces 3!], are so arranged that the emerging beam of parallel rays isspread upwardly from the optical axis 3!, for the upper half of thebeam, and downwardly from the optical axis for the lower half of thebeam, it being noted that the faces 30 controlling the upper half of thebeam are reversely positioned with respect to the corresponding faces 32controlling the lower half of the beam.

The lens L is made of colored transparent material such as glass withthe upper half colored green, G, and the lower half colored red, R.Thus, the light emitted from signal S is composed of a beam whichspreads upwardly and downwardly in a vertical plane and is colored greenfrom the optical axis upwardly, and red from the optical axisdownwardly. Also the beam is spread horizontally through a suitableangle by the lens outer curved face. Accordingly, as the signal S isrotated, it forms a cone of light for signalling to approaching planes,and the elevation of the beam is so arranged as to maintain the lowerborder of the green zone, G, a safe minimum distance 33 above thevarious hazards encountered by a plane as it approaches the airport.

Furthermore, the signal constitutes a beacon of the flashing type, andis rotated at a frequency distinctive of the particular airport withwhich it is associated, as, for example, fifteen revolutions per minute.Thus, the beacon identifies the airport and constitutes a light path ofa distinctive color, so that an approaching plane need merely passthrough the lower red zone, R, until it enters the green zone, G. Atthis point the pilot knows that he is suificiently high enough to avoidvarious obstacles and need merely glide downwardly toward the airportwithin the green zone, and preferably along the lower border .of thegreen, where it verges on the red and becomes a distinctive grayishcolor.

Upon reaching the landing field, the pilot will receive instructions asto what lane he should use for landing his plane, and the presentinvention provides means for facilitating identification of this runwayand landing of the plane on the designated runway.

As referred to above, each runway, such as the one 5, shown in Fig. 5,has a plurality of signals as l2 and i3 spaced from each other andpositioned preferably along the longitudinal center line of the runwayand directed outwardly toward an approaching plane. Each of thesesignals can be constructed, in general, as described in connection withsignal S so far as regards its optical characteristics. These runwaysignals, however, are stationary instead of being rotatable as is thesignal S, and hence, involve no motor or cam and associated parts. Therunway signals include parabolic reflectors, with suitable light sourcesand a two-colored lens colored green and red, as described in connectionwith signal S.

For facilitating identification of the landing runway to be employed atany one time, apparatus is provided for intermittently energizing thesignals for but one runway at any one time, whereby to provide signalsof characteristic colors flashing at distinctive rates.

In Fig. 7 is shown one circuit arrangement for controlling the runwaylights. The lights for each direction on each runway are connected inmultiple to individual energizing wires. For example, signals 52 and [3,which are positioned in runway 5 for east bound planes are energizedthrough a line Wire 40, while the other pairs of lights only some ofwhich are shown, are energized through other individual line wires, as4|, 42 and 43. Each energizing wire, as 40, is connected to anindividual backcontact, as 44, and the various back contacts .areconveniently arranged in an are so as to be passed over successively byafront contact 46, which is normally spaced above the back contact, andis operated by a rotatable and depressible control switch SW. Thus, thecontrol switch can be rotated to be positioned above the back contactwhich it is desired to select and then can be depressed against thefriction of a catch 69 to be retained in depressed position until movedtherefrom by the catch 60 cooperating with a groove 6| in the switch.

The front contact 46 constitutes a part of a switch arm, which includesa contact 41 separated from contact 46 by insulation or the like 62, andhaving a flexible finger 63 for making contact both before and after thedepressing of the switch, with a motor control sector 64, as shown. Itcan be noted that sector 64 makes contact with fingers '63 before frontcontact 46 has reached a position above the first back contact 44 forthe light control.

The light control front contact 46 is connected by means of Wire 56 toone contact 48 or an interrupter contact arrangement having acooperating contact '49 which is normally spaced from contact 48, butwhich is closed on contact 48 when operated by any one of the rises 56on a coding wheel ill. The coding wheel 5| is connected to an operatinmotor 52, which-can be of any desired type of constant speed motor, suchas a synchronous motor or a constant speed direct current motor.

As shown in Fig. 5, the inner signal l2, has an outer lens which is redand green with the red positioned above the green, while the outersignal l3 has a lens colored red and green, but in this case the lens isrotated 180 so that the upper portion is the green, and the lowerportion is the red. As shown, the signals are so arranged that the beamsfrom the two signals overlap to constitute diiferent distinct colorzones for a plane traveling horizontally above the air field and cuttingthrough the beams and are tilted at an les to constitute a suitableglide path and to clear obstructions, if any, such as tree m by a safemargin, 33.

The path of an approaching plane, as 35, of Fig. 2, is continued afterthe plane reaches the landing field along a path which can bediagrammatically represented as 36 of Fig. 5. It can be seen that tocontinue to travel along a horizontal line, such as 31, a planeapproaching the airport first encounters a red zone, B, or, in otherwords, the pilot sees a single red light. As he continues along thisline 31 he encounters a G/G zone and sees a green light over a greenlight. Next, he encounters a red light over a green light, or an R/Gzone, and further progress brings him an R zone, where he sees a singlered light.

The signals 12 and i3 constituting the signal means for a particularrunway are so arranged that the zone G/G forms a descending glide path,so far as possible, of the ideal angle for proper landing of the plane,while the first R zone encountered, as described above, extends to theground to leave no open danger zone near the ground.

Accordingly, upon circling the field, the pilot need merely sight asingle red light upon which he can approach horizontally toward theairport, and after entering the R zone, he knows that he must continuehorizontally and not lose elevation, since he knows that he is below theglide path zone (3/ G. Upon continuing, he enters the glide path zoneand then need merely follow this zone to land certainly and safely andat a suitable point and without danger of overshooting his mark andrequiring a further circling of the field and further attempts to land.

As the pilot glides to a landing in the glide zone G/G, should he glidetoo steeply, he will encounter the zone B and will know that he mustdecrease his angle. he glide less steeply than proper, he encounters thezone R/G, or R, according to his then elevation, which apprises him ofthe fact that he must increase his angle. The two limiting red zones, R,are so widely spaced from each other that there need be no confusion inthe mind of the pilot as to whether he is above or below the glide zonepath (3/ G.

Furthermore, should it be desired, these limiting zones, described asred, can be of different colors. To effect this, it is merely necessary,for example, that the signal l2 should have a lens showing yellow overgreen, that is Y/ G, and the signal it a lens showing green over red,that is G/R. With this arrangement, at certain elevatlons the glide pathis green over green, G/ G, with the zones beyond this path yellow overgreen and yellow, i. e. Y/G and Y, and the zones before this path greenover red and red, i. e. G/R and R. Other colors could be employed ifdesired, such as a signal l2 showing R/ G, and a signal l3 showing G/Y.

Signals S, [2 and i3, etc. have been represented wholly diagrammaticallywithout showing details of construction and adjustment, etc., since itappears unnecessary, for the purpose of the disclosure, to enter intothese refinements. It is to be understood, however, that a suitable,commercially acceptable signal will be employed, and the construction ofthe same can follow the lines of On the other hand, should 6 the signalas disclosed, for example, in the patent to Moore, No. 2,239,336,granted April 22, 1941.

With the system of airplane tralhc control as described above, it isclear that the approach of a plane to an airport, under conditions oflow visibility, and the landing of the plane at the port, has beengreatly facilitated and safeguarded, and particularly so in the casethat the country surrounding the port is of a character to presenteither natural or man-made hazards. These hazards can be safely avoidedby the pilot, by sight, under conditions of good visibility, but whenvisibility is poor, the present system furnishes means for handlingplanes with a safety and facility which is substantially equal to whatcan be accomplished under good visibility conditions.

In Figs. 8 and 9 is shown a modified form of the invention, whereinadditional landing lights are employed. Merely by way of example, thereis shown a landing runway i2 having lights I2 and 3 spaced lengthwise ofthe runway, as described above. In addition to these two lights thereare employed two other lights Hi and ii spaced crosswise of the runway.These lights are of the same type of runway lights as described above,and are controlled in the same manner. That is, in the case of the formshown in Fig. 8, the four lights I2 I3 Ill and H constitute a groupseparate from other light groups for other runways, and are to becontrolled in the same manner as described above in connection with Fig.7 for the groups of landing runway lights each of which group includesbut two lights.

The lights I2 and I3 emit beams as described above of the colors red andgreen and arranged as shown in Fig. 5.

The lights 19 and ill have a vertical division line between the twodifferent colored beams emitted from each light, and the beams are redand green as shown in Fig. 8 and overlap as shown, with the two greenbeams to the inner side.

With this arrangement, it can be seen, a glide path is defined not onlyby limiting zones above and below it, but by limiting zones to the rightand to the left of it. Thus, the glide path which constitutes not only agreen light over a green light, but also a green light to one side ofanother green light, forms a sort of tunnel, defined on four sides bydifferently colored zones. The green zone from the two longitudinallyspaced lights approximately coinciding with the green zone delined bythe transversely spaced lights.

As seen in Fig. 9, to the left of this green glide path is a red lightto the left of a green light, while beyond this is a red light, and tothe right of the glide path is a red light to the right of a green lightwith a red light beyond this. This type of glide path which is definedon four sides is more accurately defined and diiferently defined. thanthe one described in connection with Fig. 5, which latter is definedmerely in a vertical plane, and in many cases this second form hasadvantageous uses over the simpler form.

The various landing lights described above have been described inconnection, generally, with an airport, but it is obvious that all ofthem can be used in other connections, if desired, without departingfrom the scope of this invention. It is possible a situation might arisewhere several obstructions surrounded a flat open space whichconstituted a portion of a much traveled route, and in such case, arotating beacon of the form shown in Fig. 2 could be used to advantage,al though this open space need not be a landing field at all.

;In regard to the runway lights, it is entirely possible that it mightbe desirable to use them in defining sections of routes which arelimited both horizontally and vertically, as, for example, in followinga route between steep hills on each side thereof, or following a canyon.In such case it is desirable, not only to maintain the plane at a safealtitude, but also to .maintain the plane "within safe limits in ahorizontal direction. Also, it is possible that routes might beconnected by .cross routes passing through mountain passes or deepnarrow valleys, defined by steep hills at each side, and in such case,guiding lights such as described in connection with landing runways ofthe form both of Fig. and Fig. 8, might be used to advantage, and suchuse is contemplated by this disclosure.

.It should be noted that the combination of a rotating beacon having amulti-colored light beam for indicating the safe approach from alldirections to an airport having variable height obstructions has beendisclosed and claimed in .the divisional application Ser. No. 792,811filed December 19, 1947; and no claim is intended to :be made herein tosuch subject matter.

The above rather specific description of the several forms which thepresent invention can assume, has been given solely by way of exampleand is not intended, in any manner whatsoever, in a limiting sense. Itis intended that all such variations, modifications, and adaptations, asmay, from time to time appear desirable, be incorporated in the presentinvention without departing from the scope and spirit of this invention,except insofar as it may be limited by the appended claims.

Having described my invention, I new claim:

1. In airplane control systems, for use on landing .field runways,visual signal means including .two light signals, positioned in line inthe runway and spaced from each other and positioned vto-face outwardlyof the runway, each signal in- .cluding means for emitting an upper partbeam of one color, and a lower part beam of a difierent color, the upperpart beam of the outer signal being of the same color as the lower partbeam of the inner signal, and mounting means for directing said signalsso that their beams overlap on an upwardly inclined path, so that thezone common to said lower and upper part beams defines a suitablyinclined safe glide path for a plane landing on the runway. 1 ,2. Inairplane-control systems, for use on landing field runways, visualsignal means for each runway including two light signals directedoutwardly of the field, positioned in line in the runway and spaced fromeach other, each signal havingfmeans causing it to emit a beam of onecolor and spreading upwardly from the optical axis of the signal and abeam of a difierent color and spreading downwardly from the optical axisof the signal, the outer signal having its upper beam of the same coloras is the lower beam of the inner signal, and means for supporting thetwo signals in such positions as to cause their beams-to overlap in anupwardly inclined :path with their optical axes substantially parallelwhereby to define a colored landing glide path by the zone common to thesame colored beams of the two signals.

3. In airplane control systems, for use on landing field runways, visualsignal means including two light signals facing outwardly of andpositioned in line in the runway, and spaced from each other, eachsignal having means causing it to emit a beam of one color and spreadingupwardly from the optical axis, and a beam of a different color andspreading downwardly from the optical axis, the outer signal having itsupper beam of the same color as the lower beam of the inner signal,means for supporting the two signals in such positions as to cause theupper .beam of the outer signal to overlap both beams of the othersignal and to cause the lower beam of the other signal to overlap bothbeams of the outer signal with the optical axe of said signals beingsubstantially parallel to each other by extending in an upwardlyinclined direction whereby'to define a landing glide path by the zonecom- .mon to the same colored beams from the two signals, and an upperwarning zone and a lower warning zone, respectively above and below saidglide path, the upper zone appearing to an approaching plane as said onecolor over said other, and the lower zone, appearing as said other colorover said one color.

4. In a system for landing planes at an airport having at least onerunway, a first light signal unit located on said runway and beingcapable of projecting a light beam of one distinctive color above itsbeam axis and. a different distinctive color below its beam axis, meansfor mounting said first light signal to project its beam along saidrunway at an angle from the horizontal suitable for landing a plane, anda second light signal unit located on the runway spaced outwardly fromsaid first unit and being capable of projecting a light beam of saiddifferent distinctive color above its beam axis and a said onedistinctive color below its beam axis, means for mounting said secondlight signal to project its beam along said runway towards said firstunit at the same angle from the horizontal as said first unit, wherebythe upper portion of the beam of said first unit and the lower portionof the beam of said second unit overlap to provide a continuous glidepath indication of correspondin color and having substantially parallelboundaries withdistintive indications above and below such glide path toaid a plane in following the path to said runway.

5. In a system for directing airplanes in landing on an airfield runway,two pair of light projecting units directin their light beams along therunway in the direction from which an airplane is to land, each of saidunits causing its light beam to be differently colored on opposite sidesof a beam axis, means mounting one pair of said units so that theircorrespondingly colored beam portions overlap and their beam axes formboundaries on opposite sides of said runway, and other means mountingthe other pair of said units so that their correspondingly colored beamportions overlap and their beam axes form the upper and lower boundariesof a safe landing course inclined downwardly toward said runway, wherebyan airplane may safely land by following a light beam of a particularcolor and will be given a distinctive indication of a difierent coloredlight beam if it leaves the defined safe course.

6. In a system for directing airplanes for landing on an airfieldrunway, two laterally spaced light projectin units, one on each side ofthe runway, and each including means for projecting a light beam of onecolor on one side of its beam axis and a different distinctive color onthe other side of its beam axis, means for mounting said units so thattheir beam axes are substantially parallel to said runway and in suchrelationship as to cause their two beams to overlap with respect tocorrespondingly colored portions to thereby give a distinctiveindication along the runway as compared to the indication to either sideof the runway, two other light projecting units longitudinally spacedalong the runway and each including means for projecting a light beam ofsaid one color on one side of its beam axis and said different color onthe other side of its beam axis, and means for mounting said two otherlight projecting units so that their beam axes are substantiallyparallel to each other and in such relationship as to cause their twobeams to overlap with respect to correspondingly colored portions andwith their beam axes extending with a rising angle with respect to thelevel of said runway but with their beam axis planes at right angles tothe beam axis planes of said two laterally spaced units, whereby anairplane can safely descend to said runway by following said distinctiveindications as provided by said longitudinally spaced light projectingunits determining the upper and lower boundaries of a safe landingcourse with said laterally spaced light projecting units giving adiflerent indication if the air- 5 plane deviates to either side of saidsafe landing course.

SAMUEL P. SAINT.

10 REFERENCES CITED The following referenlces are of record in the fileof this patent:

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